The present invention relates to an apparatus for accurately positioning read/write heads of a magnetic read/write unit very precisely relative to the closely packed data tracks of the magnetic tape to insure that data is written onto, or read from, a desired select track. Since the data and tracks run parallel to the length of the tape (i.e., parallel to the transport direction), the read/write head must be moved in both directions (e.g., up and down) perpendicular to the transport direction.
A device for positioning a magnetic head relative to tracks of magnetic tape in a magnetic tape read/write unit is described in U.S. Pat. No. 4,491,890 and U.S. Pat. No. 4,609,959. With this known arrangement, the positioning of a magnetic head occurs by the employment of a worm drive and a screw drive connected to a drive motor which can be a DC motor or stepping motor.
In U.S. Pat. No. 4,609,959 a magnetic head disposed on a magnetic head carrier is positionable by means of a worm drive means and a screw drive means wherein the worm drive is formed of a worm spindle gear driven by a drive motor and associated with a worm wheel gear, and the screw drive is formed by an inside thread of the worm wheel and an associated outside thread on a shaft. The shaft is mounted in a fixed manner to the housing frame of the tape recorder. The magnetic head carrier is arranged so as to be displaceably disposed on the shaft and non-positively connected to the worm wheel, thus securing the magnetic head carrier against rotation during the rotation of the worm wheel, but allowing the head carrier to follow the axial motion of the worm wheel.
It is advantageous to provide a reliable mechanism for rapid, reliable fine tuned positioning of a magnetic head with respect to magnetic tape tracks.